1. Field of the Invention
The present invention relates generally to a control and actuation system for a baking-in-a-mold apparatus for producing molded preforms which, upon release from the mold, become expanded-grain cakes. More particularly, the invention relates to an improving of the control system by incorporating multiple parameter sensors and multiple actuators.
2. Description of the Prior Art
Generally, an apparatus for producing expanded-grain cakes is a molding machine in which a predetermined charge of admixed cereal grains is inserted into a hermetically sealed mold cavity thereof and subjected to pressure baking by a predetermined cycle of temperature. The product of the molding machine is a preform or molded cake. During baking the moisture content of the cereal is converted into entrapped steam and, upon rejection from the mold cavity, the entrapped steam from the treated charge of grain expands the molded cake to an expanded grain cake of the desired size.
As will be seen from the following, the machine control and actuation subsystems enhanced hereby include, but are not limited to, the grain feed and controls therefor, the preheating of the mold cavity, the monitoring and maintenance of mold temperature and pressure, and the control system interrupts of the molding process when an error or component malfunction occurs.
In detail, when an appropriate charge of cereal grain is sealed in a mold and heat is applied thereto, the grain expands to a preform constrained by the walls of the mold and entrains therewithin the moisture content of the grain in a gaseous, high-pressure state. Thereafter, when the mold which had been sealed opens, the high-pressure gas in the preform suddenly expands until it reaches ambient pressure and, acting as a blowing agent rapidly expands several fold to produce the expanded grain-cakes of the desired size.
In the past, the machines that were introduced for producing expanded-grain cakes experienced numerous problems that were seemingly inherent to the accepted design at the time Of prominence among the problems was that the shapes of produced expanded-grain cakes were not uniform. Particularly this problem seemed to arise in those machines wherein the supply of cereal grains and the clamping of the mold were provided by the single-drive unit machine. After such a machine was used over an extended period of time, the amount of the charge of cereal grain tended to become non-uniform as errors accumulated. Also and concomitantly, the charge of cereal grain was not spread evenly in the mold cavity resulting in misshapen preforms and lopsided expanded-grain cakes. The early prior art machines did not program the delivery of thermal energy and, once the heat was delivered, were unable to maintain the pressure in the closed-mold unit. Both of these factors contributed to non-uniformity.
Furthermore, with such errors accumulating due to insufficient parameter monitoring and control, and an insufficient amount of cereal grain being supplied to the mold, the clamping operation during the closed-mold phase frequently occurred when the grain transfer unit was not completely removed from the mold. If not stopped in time, this potentially could result in damage to the grain-transfer unit.
Moreover, the prior art machines had no means for preheating the mold. Hence, when thermal energy was underdelivered the process in the mold did not sufficiently heat the contents and resulted in insufficient generation of blowing gases. Under such conditions, some of the cereal grains supplied to the mold would remain therein as there was an insufficient volume of gas to clear the cavity.
The remnant cereal grains in the mold cavity frequently became scorched, burned, and discolored resulting in a contaminated mold. Until all the burned grain was removed from the mold the expanded-grain cakes produced by the contaminated machine was not of marketable quality.
In the prior art machines, to solve these problems, an operator, upon opening the mold unit, would clear the mold cavity of debris using a tool such as a brush or the like. However, as such cleaning was conducted with the mold at a high temperature, the cleaning was performed under unsafe, hazardous conditions.
Furthermore, in most prior art machines, the hopper was integrated with the machine and the operator had no visual cue as to the amount of cereal grain remaining. Because the hopper was typically made of stainless steel the user could not observe the amount of cereal grain in the hopper. Without sensors to set off interrupts, such a machine may be operated through one or more molding operations without sufficient cereal grain in the mold and thereby expose the machine to unnecessary downtime.
While the above recitation of problems inherent in the prior art machines is remarkable, it clearly is not an exhaustive collection hereof. However, these and other problems resulted in certain technological re-evaluations being made prior to the present invention. During re-evaluation, the state-of-the-art was examined and the following discussion is of the patent literature which has become known to the inventor and the assignee hereof.
In the prior art a number of machines of this type have been developed that include heated mold components which during operation are moved away from one another for loading of a predetermined charge of cereal grain and for unloading a baked product. Such machines were commonly developed in the Pacific Rim countries such as South Korea and Japan where rice cakes play an important role in the diet.
U.S. Pat. No. 7,444,928 to Kim (Kim '928), entitled “Apparatus for Producing Crackers”, discloses an apparatus capable of mechanically producing expanded-grain cakes. The patent is a non-priority filing of Korean Patent 10-571883, filed Mar. 9, 2004. The Kim '928 apparatus has a single drive motor and, through transmitting the rotary power thereof using power takeoffs and cams, was able to replace the air cylinders and air compressors which sequenced the operations of earlier machines. The controls are simply disclosed as “a control box” with no functional detail taught, and no mention is made of any sensors in the apparatus. The resultant machine did not have sufficient fail/safe features as is apparent when the invention described below is understood.
The patent to Yoshikazu, U.S. Pat. No. 4,328,741, issued May 11, 1982, is an air cylinder operated molding machine which is distinguished from prior devices as the machine did not require bonding agents in the charge of cereal grains. Yoshikazu describes twice molding the grain cakes by first pressure baking and expansion and, then compressing the expanding cake to achieve the desired form. Yoshikazu teaches the use of control means including multiple timers and limit switches, but no use of programmable controls or sensors with functions other than on/off.
During the 1970's and 1980's, Gevaert obtained several patents on expanded cereal-based food product machines. Typical of the Gevaert patents is U.S. Pat. No. 4,281,593 which describes a molding machine with a hydraulic jack that raises and lowers a lower mold portion to close and open the mold, respectively. The precooked cereal grain is further cooked in the closed mold and gains its final shape by, after releasing the steam from this process, moving the upper mold downward to release the compressed and treated material. Nothing in the way of electronic controls or sensors is disclosed, and neither is any electric motor disclosed.
A patent to Van den Berghe, U.S. Pat. No. 5,102,677 describes making a pressure baked, cereal grain cake in a heated mold and, afterwards, upon release from the mold, expands. Van den Berghe discloses two different molding units—a two-part mold in which hydraulic cylinders drive mold components to selected positions, and a three-part with a fixed upper, a positionable peripheral or ring mold, and a heatable removable lower mold. In the three-part mold, the downward positioning of the ring mold and the lower mold permits the removal of the expanded grain cake. The use of a programmable control unit is taught, which in combination with limit switches serves to control the sequence and range of motion of the actuators in the molding units. However, the control unit is not shown in the Figures and although there is disclosed control means for monitoring and adjusting the mold temperature, operation of the ingredient feeder, and the operation of the actuators, no specifics are taught and no electric motors or sensors other than on/off are used.
The above prior art developments are exemplary and provide a background against which the advances presented by the below-described invention may be viewed.